Method of casting composite metals



Dec. 2, 1941. w. ROTH 2,264,457

METHOD OF CASTING COMPOSITE METALS Filed March 27, 1959 2 Sheets-Sheet 1 5515.1. fig.. 5..

.Dec.2, 1941. w. ROTH 2,264,457

METHOD OF CAS' IING COMPOSITE METALS Filed March 27, 1939 2 Sheets-Sheet 2 lfl Patented Dec. 2, 1941 UNITED STATES PATENT OFFlCE H METHOD or oasrme COMPOSITE METALS Walter Roth, Buschhutten, near Kreuztal, Westphalia, Germany,'assignor to Vereinigte Leichtmetall-Werke Gesellschaft mit beschrankter Haftung, Hanover-Linden, Germany Application March 27, 1939, Serial No. 264,279 In Germany May 12, 1937 5 Claims.

casting and cooling metal ingots, particularly ingots formed of aluminum alloys, was disclosed in which irregularities ordinarily appearing in the casting of an ingot are avoided by casting the metal ingot in a thin sheet metal mold, and cooling the ingot substantially immediately after the same is cast by conducting the heat inthe ingot through the metal mold wall anddissipating said heat by means of a water bath or water spray. The metal mold is formed of thin metal sheets which are arranged to have at least one side open,

a pouring spout being inserted through said open i got increases in height during the pouring thereof. The metal sheets used for forming the mold can be of the same metal as the ingot poured, or of a different metal, and can be welded to the ingot by reason of the heat of the molten metal. The thus plated ingot can be rolled into its final form. v

It is an object of the instant invention to improve upon the process disclosed in application Serial No. 206,880. 1

Another object of the invention is to make an improved process for welding the metal sheets forming the mold to the molten material in the mold.

A further object of the invention is to regulate the time between the pouring of the metal in the ingot and the cooling of the ingot through the metal walls of the mold so that the metal walls of the mold have an opportunity to become thoroughly welded to the ingot metal.

Another object of the invention is to cast a metal ingot in a sheet metal mold, the walls of which are to be united'to the metal of the ingot by welding. I

1 Another object of the invention is to cast a plated ingot in a continuous casting and cooling process so regulated that the metal plating sheets which form the mold walls are united by welding to the metal in the ingot, while. at the same time, they are prevented from being melted by the molten ingot metal.

Another object of the invention is to provide a process in which a relatively large metal ingot can be poured into a relatively thin sheet-metal mold andwelded thereto by welding without melting said thin sheet metal mold.

Generally, these objects are obtained byusing the same type of mold'as shown in application Serial No. 206,880, but during the pouring of the ingot, a certain period of time is allowed to elapse between the pouring of the molten metal into the mold and the time when the heat is being conducted 011? from the ingot, as by immersion in the water .bath. v

The means by which the objects of the invention'are obtained may be understood more readily by reference to the following specification, taken in connection with the drawings; in which;

Fig. 1 is a vertical cross sectional view of one format the invention.

Fig. 2 is a cross sectional view taken at right angles to Fig. 1.

Fig. 3 is a plan Fig. 1.

Fig. 4 is a plan view of a modified form of the invention.

Figs. 5, 6 and 7 are views similar to Figs. 1, 2 and 3, respectively, of a further modified form of the invention; and,

Fig. 8 is a cross sectional view of the mold being lowered into a water spray cooling device.

Similar reference characters refer to similar parts in all the various figures.

The apparatus and mold employed are the same as shown and described in application Serial No; 206,880. Thus, clamping and closure members I are provided for holding together the free ends of the sheet metal walls 2 which form the mold, and which are to be welded to the fin-' ished ingot. 'Mold 2 is supported by table 4, which tabl is adapted to be lowered into a water view of the invention shown in bath 6. The pouring spout 3 has its end in con- I tinual contact with the melted sump of a partially formed ingot 5.

When the mold is first erected, the table is slightly above or approximately flush with the surface of the cooling bath. Metal walls 2 forming some of the sides of the mold are placed on the table and are first clamped together by means of the lowermost of the fastening elements or segments I. These block-like segments are fiat and preferably slightly inclined toward the mold, and clamp together and reinforce the two free ends of the thin sheet metal walls 2. Elements I are made of any desired material, either metal or ceramic, and if heavy enough, are sufficient to clamp the walls of the mold 2 together while sealing the opening between the free ends of the wall. Additional fastening means may be provided if desired.

Figs. 1, 2 and 3 show the thin metal wall 2 composed of a single sheet of metal bent into U-shaped form, the single open side being closed by segments i. In Fig. 4, the metal wall 2 is bent into circular, rather than U-shaped form.

In Figs. 5, 6 and 7, the metal wall is composed of two spaced thin metal sheets open at two sides, each of the open ends being closed by segments I. As shown in Fig. 5, the closing segments on one side can be built up in advance of the other side through which the pouring spout extends. Alternatively',.the segments can be built up at the same rate on each side and a pouring spout can extend through each side, accelerating pouring thus being obtained.

Fig. 8 discloses the lowering of the table with the mold thereon into the range of a spray apparatus .1. Such spraying apparatus can be used in place of the water bath 6 shown in Figs. 1 to 'I.

When the pouring begins, the metal flows through the spout 3 and immediately forms a puddle on top of the table 4 within the confines of the mold. The mold is lowered at a rate sufficient to keep the pouring .'end of the spout in continual contact with the poured metal. As the ingot grows, additional segments i are placed one on top of the other in, advance of the height of the growing'ing'ot, .and as the table is being continuously lowered. Thus the spout 3 does not need to be moved, and the segments are'built up in proportion to the rate of the lowering of the table. In application Serial No. 206,880, th'eingot is described as being lowered into the cooling bath substantially immediately after the metal has been poured into the mold. It has been discovered by the instant invention that a better welding between the metal of the ingot and the metal walls of the mold can be obtained by allowing a short period of time to elapse from the moment of pouring the metal in the mold to the moment when the metal is cooled by immersion in the water bath or cooling spray. During this time interval, the molten metal in the mold will heat the thin metal sheets to a point where intimate welding takes place between the metal sheets and the metal of the mold. ,The mold is then lowered into the cooling device, before the metal walls are heated to their melting point, and solidification takes place rapidly over the whole cross section substantially in a horizontal planeas the heating metal is being cooled through metal wall! in the cooling device.

For example, a metal ingot composed of an aluminum alloy of the Al-Cu-Mg type is poured into a mold composed of thin sheet metal walls 2 of pure aluminum, said walls having a thickness from 5% to 10% of the total thickness'of the ingot. The molten ingot metal is poured at a temperature of about 660 to 680 C. The table 4 is lowered at a rate of about 100 mm. per minute, the pouring rate of the metal through the spout 3 corresponding to the rate of lowering the table. From two to four minutes are allowed to elapse yet immersed in the cooling device the thin the ingot, with the advantages of having not from the moment of pouring the molten ingot metal to the moment in which the poured portion of the ingot is immersed in the cooling bath, the

sheet metal walls conduct ofl heat from the metal ingot so that a substantially solidified portion 5a, with a thickness a little thicker than that of the metal sheet, is formed. As the metal sheets 2 are, in practice, about 9 mm. thick, solidified portion 5a of the ingot adjacent the metal sheet is from 10 to 15 mm. thick. The metal sheets at this time are heated by the molten metal to a temperature about 500 0., which is below the melting point of the metal in walls 2, but high enough to allow the walls to become welded to themetal in the ingot. solidified portion 5a of the ingot remains substantially constant until that portion of the ingot reaches the cooling device. Inasmuch as it takes from two to four minutes for this portion of the ingot to reach the cooling bath, an intimate welding between the sheets 2 and the metal in the ingot takes place between the ingot metal 5 and the sheets 2 at their point of contact, while, at thesame time, the metal walls are not exposed to the heat of the poured metal long enough to be raised to their melting point, this being of particular advantage in the pouring oflarge ingots wherein the mass of molten metalis' easily suincient to bring the thin metalsheets to their melting temperature.

As the ingot is immersed into the cooling device, a very rapid solidification takes place substantially in the upward direction, and the metal walls are cooled whilewelded'to the ingot. In view of this rapid solidification, segregations and other imperfections in'the formation of the ingot are substantially precluded, while, at the same time, the advantages of fine grain and density of structure are obtained.

It is thus seen that the invention obtains an improved process of welding or uniting thin plating materials to an ingot during the casting of only the improved unification between the plating material and the ingot, but also of having an improved ingot structure. It is clear that by following the steps of this simple process, that is, of pouring the metal into a mold composed of thin sheet metal walls which form a plating material, allowing the metal to stand in the walls a short time to allow welding to take place between the metal walls forming the mold and the material in the moldgand then rapidly solidifying the metal'inthemold by conducting heat through the thin sheet metal walls, an improved process of continuously pouring and plating an ingot, and an improved plated ingot is obtained.

= Having now described a means by which I obtain the objects of my invention, what I claim is:

1. A process for the production of plated ingots by the cast-plating method in which the mold becomes a part of the completed ingot comprising mounting upon a pouring table at least one self-sustaining thin sheet metal plate which is adapted to form both the mold for and the plated walls of the cast ingot. at least two edges of said plate being spaced to form a vertically extending opening for a pouring spout, continuously pouring molten metal into the mold from said spout while lowering said table so that the top surface of said molten metal within said walls stays in substantially the same plane and while closing said opening in advance of the poured metal by members extending between and engaging said edges, maintaining successively poured portions of said poured metal in molten state until welding takes placebetween said portions and their adjacent wall portions, and then solidifying said poured metal and said metal portions welded to said walls by directly cooling said walls in a cooling device.- I l 2. A process as in claim 1 in which said poured portions are partially solidified against said wall portions while bringing said wall portions to, welding temperature.

3. In the process of casting a plated ingot comprising pouring molten metal through a slot in a mold while simultaneously lowering the mold,

closing said slot, and solidifying the metal in the mold; the steps of forming a mold cavity at least one wall of which consists of a self-sustaining thin metal sheet, which is adapted to become a plated surface of the ingot, pouring molten metal in said mold while lowering said mold so that the top surface of the molten metal within said mold stays in substantially the same plane, maintaining contact between the poured molten metal and said well while lowering said mold until said molten metal is substantially solidified to a thickness slightly greater than the thickness of said wall, while at the same time said metal heats said wall to cause welding between the substantially solidified metal and said wall, and then solidifying the entire thickness of saidingot by lowering said ingot into a cooling device.

4. In the process as in claim 3, said wall composed of said thin metal sheet having a thickness ranging from 5% to 10% of thetotal thickness of the ingot. f

5. A process for the production of plated metal ingots by the cast-plating method, comprising mounting upon a pouring "table at least one thin sheet metal plate which is adapted to form both the mold itself and the plated walls of the cast ingot, at least two edges of said plate being spaced to form a vertically extending opening for a pouring spout, continuously pouring molten metal into the mold from said spout while lowering said.

table and while closing said opening in advance of the poured metal by members extending between and. engaging said edges, maintaining successively poured portions of said poured metal in molten state until welding takes place between said portions and their adjacent wall portions, and solidifying said poured metal by directly cooling said walls at a distance ranging from approximately 200 mm. to 400 mm. beneath the top surface oi the molten metal.

WALTER ROTH. 

